The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
During a combustion cycle of an internal combustion engine (ICE), air/fuel mixtures are provided in cylinders of the ICE. The air/fuel mixtures are compressed and combusted to provide output torque. After combustion, pistons of the ICE force exhaust gases in the cylinders out through exhaust valve openings and into an exhaust system. The exhaust gases may contain oxides of nitrogen (NO.) and carbon monoxide (CO) and hydrocarbons (HCs). The exhaust gases may also include methane (CH4) depending upon the type of fuel combusted. For example, CH4 is produced when ethanol C2H5OH is combusted.
An exhaust gas treatment system of the ICE may include one or more catalytic converters to reduce exhaust emissions. As an example, a four-way catalyst converter (FWC) may be used to reduce NOx, CO, HCs and CH4 within an exhaust system. The FWC converts NOx to nitrogen and oxygen, CO to carbon dioxide, and oxidizes HCs and CH4 to produce carbon dioxide and water.
A catalytic converter typically does not prevent pass through of methane gas until heated to temperatures greater than or equal, for example, 600° C. At temperatures below 600° C., methane gas can pass through a catalytic converter without being converted. This can occur, for example, during a cold start of an engine. As a result, a catalytic converter does not function to convert methane and/or provides minimal methane emissions reduction while temperatures of the catalytic converter are less than a minimum active converting temperature for methane.